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Decoherence spectroscopy with individual two-level tunneling defects

Lisenfeld, Jürgen; Bilmes, Alexander; Matityahu, Shlomi; Zanker, Sebastian; Marthaler, Michael; Schechter, Moshe; Schön, Gerd; Shnirman, Alexander; Weiss, Georg; Ustinov, Alexey V.



Abstract (englisch): Recent progress with microfabricated quantum devices has revealed that an ubiquitous source of noise originates in tunneling material defects that give rise to a sparse bath of parasitic two-level systems (TLSs). For superconducting qubits, TLSs residing on electrode surfaces and in tunnel junctions account for a major part of decoherence and thus pose a serious roadblock to the realization of solid-state quantum processors. Here, we utilize a superconducting qubit to explore the quantum state evolution of coherently operated TLSs in order to shed new light on their individual properties and environmental interactions. We identify a frequency-dependence of TLS energy relaxation rates that can be explained by a coupling to phononic modes rather than by anticipated mutual TLS interactions. Most investigated TLSs are found to be free of pure dephasing at their energy degeneracy points, around which their Ramsey and spin-echo dephasing rates scale linearly and quadratically with asymmetry energy, respectively. We provide an explanation based on the standard tunneling model, and identify interaction with incoherent low-frequency (thermal) TLSs as the major mechanism of the pure dephasing in coherent high-frequency TLS.


Zugehörige Institution(en) am KIT Institut für Theoretische Festkörperphysik (TFP)
Physikalisches Institut (PHI)
Publikationstyp Zeitschriftenaufsatz
Jahr 2016
Sprache Englisch
Identifikator DOI: 10.1038/srep23786
ISSN: 2045-2322
URN: urn:nbn:de:swb:90-539512
KITopen ID: 1000053951
Erschienen in Scientific Reports
Band 6
Seiten 23786
Bemerkung zur Veröffentlichung Gefördert durch den KIT-Publikationsfonds
Schlagworte Quantum information; Qubits; Surfaces, interfaces; thin films
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